It is known to fabricate booklets with a starting point from covers of the kind in question. Such covers and methods of booklet fabrication with a starting point from said covers are described in WO 94/265 35, among other publications.
These known covers and methods enable high quality booklets to be produced in a simple and rational manner in environments which do not primarily relate to the production of booklets, folders or books. Even though the known covers and methods can be used and applied in such primary production, they are primarily intended for the fabrication of booklets which are sub-handling products, e.g. products in office environments in which different types of printing matter is to be presented in a functional manner, and which afford the greatest advantages in such production. The area of use extends from booklets that contain only a few sheets of paper to compendiums that include several hundreds of sheets or pages. The method of production enables the fabrication of booklets ranging from just a few booklets to relatively large series comprising several tens of thousands of booklets to be achieved in an economic manner with method implementations that are adapted to the size of the series intended.
However, the known covers and the methods applied in the fabrication of booklets on the basis of these covers are encumbered with a binding-agent related problem. The binding agent is comprised of a strip of adhesive material or substance applied firmly to one side of the spine of the cover, said adhesive strip or layer being brought into abutment with the bundle of paper sheets inserted between the cover sheets and the adhesive activated, e.g. , by applying heat thereto. The binding agent is therewith converted from a solid state to a molten or semi-molten state, so as to enable the sheets to penetrate into the binding agent. When the binding agent is caused to harden, the sheets are firmly anchored in the cover and therewith complete the booklet.
It has been found, however, that the binding agent is adhesive to some extent even when in a solid state, particularly when the binding agent lies against a surface over a long period of time and under a certain degree of pressure. This adhesiveness it undesirable and can cause problems in some cases. This applies in particular to the case when the covers are stored and handled while nested together in stacks, with the inner surface of the spine of one cover in abutment with the outer surface of the spine of an immediately adjacent cover and the string of binding agent in contact with said outer spine surface. This is the case when the covers are mutually nested in a V-shaped stack in the type of magazine described in the aforementioned patent specifications.
The covers are thus liable to stick together and therewith cause disturbances in production, particularly in view of the relatively high degree of mechanization employed in the use of the binding machines described in said patent specification.